Circular RNA (CircRNA) is a type of single-stranded RNA that plays a vital role in gene regulation during and after transcription. However, the functional role of circRNA in polyploid crop hybridization has not yet been reported. In this study, a high-yield elite upland cotton (Gossypium hirsutum) inbred line, 4133Bt, crossed with a high-quality elite inbred line, J02–247, produced a high -yield and high-quality F₁ hybrid. An RNA-sequence library was constructed from three biological replicates of the parents and F₁ hybrids in the vegetative and reproductive growth periods. A total of 340 high-confidence circRNAs were identified. Our results showed that the circRNAs were more active in ovules than in fiber and leaves and that the host genes of ovule-specific circRNAs were involved in nucleoside metabolic processes. In addition, single parent expressed (SPE) circRNAs and extremely nonadditively expressed (ENAE) circRNAs had different expression patterns in the F₁ hybrid. Moreover, 32 out of the 340 circRNAs were found to be dominant (expression level dominance, ELD) or overdominant (transgressive) at the expression level. These circRNAs might regulate the expression of their host genes through competitive inhibition. Eight of these 32 circRNAs might regulate gene expression through a putative ceRNA network. At 0 days post-anthesis (0 DPA) ovule, five circRNAs were found to interact with six miRNAs that are associated with the regulation of cytoskeleton- and plant cell wall-related genes during the initiation stage of cotton fiber development. Two circRNAs that interacted with two miRNAs to regulate vesicle transport and signal transduction pathways during the fiber elongation stage were identified at 10 DPA (fiber). These results indicate that circRNA may regulate the initiation and elongation stages of cotton fiber via a sponge model during the hybridization process. This study provides a deeper understanding of the molecular mechanism of hybrid breeding from a new perspective.

环状RNA（CircRNA）是一种单链RNA，在转录过程中和转录后的基因调控中起着至关重要的作用。然而，尚未报道circRNA在多倍体作物杂交中的功能作用。在本研究中，高产优质陆地棉（Gossypium hirsutum）自交系4133Bt与优质优质自交系J02-247杂交，产生了高产优质F ₁杂种。由亲本和 F _{1 的}三个生物学重复构建了一个 RNA 序列文库处于营养生长期和生殖生长期的杂交种。共鉴定出 340 个高可信度的 circRNA。我们的结果表明 circRNA 在胚珠中比在纤维和叶子中更活跃，并且胚珠特异性 circRNA 的宿主基因参与核苷代谢过程。此外，单亲表达（SPE）circRNAs和极度非加性表达（ENAE）circRNAs在F ₁杂交种。此外，发现 340 个 circRNA 中有 32 个在表达水平上是显性的（表达水平优势，ELD）或过度显性（海侵）。这些 circRNA 可能通过竞争性抑制来调节其宿主基因的表达。这 32 个 circRNA 中的 8 个可能通过假定的 ceRNA 网络调节基因表达。在花后 0 天 (0 DPA) 胚珠，发现 5 个 circRNA 与 6 个 miRNA 相互作用，这些 miRNA 在棉花纤维发育的起始阶段与细胞骨架和植物细胞壁相关基因的调节相关。在 10 DPA（纤维）时鉴定了两个 circRNA，它们与两个 miRNA 相互作用以在纤维伸长阶段调节囊泡转运和信号转导途径。这些结果表明，circRNA 可能在杂交过程中通过海绵模型调节棉花纤维的起始和伸长阶段。本研究从新的角度对杂交育种的分子机制有更深入的了解。